Filter



Aug. 20, 1946. c. G. VOKES ETAL y2,406,308

FILTER Filed Sept. l, 1 943 I -sheets-sheet 2 ffl/G2.

' Attbrney V Aug. 20, 1946. c. G. voKEs ETAL 2,406,308

FILTER Filed Sept. l. 1945 3 Sheetsf-Sheet 3 'Ilm-f l INVENTORS ATTORNEYPatented Aug. 20, 1946 FILTER VCecil Gordon Vokes and EdwardArthur'Stokes, ALon'domEngland; said Stokes assigner to Vokes",Limited;` London,` England Application 1september 1, 1943,seria1N0.500,s73 uInzGrreatBritain September 17,.,1942

rinthe specification -of pending application No.

`344,583 (C. G. Vokes) there is described a filter `in which filtrationis maintained in a parallel circuit which returns iinely lfiltered ,oilVto a reservoir or the like, even when back pressure on less ne mainflow ltering means has caused the latter to be automatically -by-passed.The

present invention provides a simple and compact construction suitablefoil' `functioning in such a manner. In its preferred forms the Vfinerand'less nefiltering means take the form of lter units mountedsubstantially co-axially in Aa common casing, the iiner filtering meansand its outlet being preferably merely ladded in an extra length or(possibly) diameter, or both of the enclosing shell of whatissubstantially `or exactly one of the present standard types of Vokes oillters embodying a unit like that of the main circuit filter shown in theabove mentioned specification. In this invention the main ow can by-passthe less ne iiltering unit completely when clogging has raised its backpressure toa predetermined value, while the ner unit is intended toremain normally fixed 'in the parallel circuit (though a safety valvemay be used to prevent excessive difference of pressure when oil or thelike is cold and until its warms up) and appropriate cleaning enables itto continue to perform a useful function almost indefinitely.

Other parts of the invention are embodied in typical forms shown uponthe accompanying drawings, the parts for which a monopoly is desiredbeing those delimited by the claims.

In the drawings:

Fig. 1 is a sectional elevation of one such form and y y Fig. 2 is asimilar View of another vsuch form.

Fig. 3 is a section on line 3 3 of Fig. '1.

Fig. 4 is a section on line 4 4 of Fig. 2.

'In each form a header is formed by a casting with an inlet connection Iand a main ow outlet connection Zand a main enclggire com- -fpleted by ashell or casing 3 secured, by a clamping ring vIl and bolts v5, againstjoining material 6.

The less ne filtering vunit is of the Wellknown form in which anappropriate deeply pleated or star-shaped screen 'I in a cylinder y8 ofperforated metal is held between end plates 9, I and carries a joint orjoints `II resiliently lpressed against the header by a spring I2. The

spring I2 bears against a diaphragm I3 which vrestson a swaged'internalbead 3a inthe shell :3 :and forms apartition which need not necesl7-claims. V(o1. V21o-164) sarily be completely fluid-tight (though -itwill preferably stop large particles rof dirt or other impurity) becausea certain amount of additional ilow in the lower chamber caused by someleakage at this'point will help to maintain an even favourabletemperature of the oil in the lter. 'I-he filter ltering unit is of aform which is the subject of a cci-pending application, iiled Septemberl, 1943, Serial No. 500,872, being built up of Ydeeply grooved discs I4of finely porous ceramic material so as to ,provide a lhollow cylinderwith deep hollouT peripheral ns giving a substantial area exposed tothe` `iiuid to be filtered and cleanable by the scraping action ofspring knives I5 when relatively rotated.

Turning now specifically to the form of Fig. l, the less fine unit hasat its inlet alguiding ltube I6 with ports I Ga. The tube I5, open atthe ends is slidably guided Ain an appropriately formed part of theheader casting, and the ports tube I 6 is -movable with the less finefilteringk element 'being preferably welded or otherwise secured to theplate 9. Obviously, when under conditions Ato be dened the less fineltering element is'lowered, the openings Ia are, in the movement of thetube I6 in position to establish communication in the interior of thetube It and the space between the `less fine ltering element and theoutlet 2 of the header. When theback pressure ofthe screen 1 is suicientto cause the unit to move against the pressure of spring I2 the fluidfrom the header inlet I passes through `the ports Ia, directly to themain ow outlet 'i 2, by-passing the screen 1. The fluid passing tovtheparallel.circuit through the liner unit lenters-a `central rod I'Iby Vports I'Ia ywhich are at least a sufficient distance above thebottom of the'less iine unit to avoid picking up accumulated dirt orsludge. 'The rod I'I passes through the header and is removably xedrelative thereto against Alongitudinal ymovement by shoulder I'Ibbearing against the header from beneath and removable securing Imeansabove theheader. 'The rod il' extends "through-its lower end. `'The krodI'I carries the filtering purposes.

driver `or squared or other suitable lower end to' `engage acomplementary part of a vspider I9 forming part of the structure thatcarries the spring knives I5. Rotation of the rod I'lv by means ofatommy-bar 2i! or other operating member outside the filter enclosurethus peis in parallel circuit, because the oil entering `the heater isdirected through the two units in parallelism. That is, a main nowcircuit through the coarser unit and a parallel flow circuit throughports I'la. The oil through the coarser filter reaches outlet 2 whilethe oil through the ner filter reaches outlet 22.-

Turning ,next to the specic form of Fig. 2,

the inlet to the less fine unit is through ports riodically cleans andscrapes away asmall surface layer of the material of the grooved discsi4. Fluid passing through the finely porousv material of thediscs'enters the hollow clamping bolt 2I by ports 2Ia and emerges at`the outlet 22. e the finer filtering unitand holds the discs I4 Yassembled between plates 23. When oil is cold a very considerable backpressure is exerted by the material ofthe discs I4V even though thesurface is kept clean by the knives and may crush or damage them. Asafety valve consisting of ball 24 and spring 25 may therefore be Y ttedto limit the diierence between external and internal pressure. Arestriction aty 2| b in the lower part of thebore of the hollow bolt 2lcauses the internal pressure to build up `and prevents mere by-passingwhen such conditions obtain. The restriction 2lb is not designed toprevent passage therethrough, but .is partcularly formed to prevent morethan a limited flow. Thus, if the normal oil pressure when the oil ishot should be, for example, lbs. per sq. in., such pressure mayapproximate 50 lbs per sqfin. when the` oil is cold. The restriction 2lbis formed to allow the internal pressure to build up to, in the examplequoted, 40 lbs. per sq. in., so that the walls of the discs I4 aresubjected only Yto a diie'rence of pressure, outside and inside, ofapproximately 10 lbs. per sq. in. When the oil is hot and the viscositylow, the ball 24 will be seated and the effect of the restriction toflow of 2lb will be so small as to be negligible.

In operation the uid enters the apparatus at the inlet I and if the oilis cold it may for a short time by-pass 4the less. fine filtering unit.While ordinarily the oil is not at a temperature to compel this by-pass,yit will under these conditions, move the ball 24k so thatrthe flow ofoil into the finer unit, through the walls of that Vunit through itsexterior Vwalls is relatively small and there will be some delivery or`by-V passing through the restriction 2lb. As the oil warms up, ball 24returns to its seat, and :the packing ring II of the coarser unit movesto its seating position, assuming that the' coarser unit has beendepressed at all in the initial ow of the cold oil. The parts are thenin the position shown in Fig. 1 and function normally for When thefilter screen 'I'is choked or clogged to the predetermined extent thecoarser unit moves down against the tension of spring I2. This does notreduce the oil pressure on the liner unit, except by thel amount of thepredetermined back pressure, say 10% of the total, since the finer unitis in circuit to the bearings or other`point of lubrication application.The ner unit continues to function and passes substantially its fullquota as long as it is kept substantially clean by the scrapingVoperation described. The inlet pressure will not suflice to lift theball 24 so long as the oil is hot. Y It will, of course, be obvious thatthe ow of oil through thecoarser'and finer units 9a from a substantiallyannular space4 la in the header. A central tube 33 connects the end`plates 9 and I0 and yby-passing takes place dil f rectly from the spacela to the main flow outlet The clamping bolt is used to mount 2 whenclogging of the screen l represents the predetermined back pressure. Theunit is mov- Y able on the fixed hollow central rod I1 4which the casingaiTords a gland at 32 and abottom v outlet at 22 for the finely filteredfluid: it supports the washer 33 on which the filter unit rotates. Theknife-carrying structure is prevented irom rotating by lugs 34 securedin the casing 3. The tube I6 of Fig.. 1 *andl the joint members Il ofFigs'. 1 and 2 obviously serve as valves for providing direct flow fromthe inlet to the outlet of the header when the less-fine filter isinoperative. While the term coarse and fine has been applied to thefiltering elements in the claims, it will be understood that the termsare used simply to distinguish the two y and are relative only. l

1. In a filter, a generally cylindrical casing having a central axis anda closed lower end, Va header closing the upper end of said casing, saidheader having internal wallY means defining Va chamber, there being aninlet in said header ,in

communication with said chamber, thereV also being an outlet in saidAheader exteriorly of said chambena partition in said casing forming rstand second compartments spaced along said axis, a coarse ltering elementin said first compartment and having a iirstrclosedrend hav- "ing anopening therein, a second/ and imperiorate end remote fromY said walland perfcrate side walls, resilient means between said second end andpartition yieldingly urging said rst end of said coarse filteringelement into fluidtight engagement with the end of said chamber Awallmeans, whereby uid passes from said inlet to said chamber, thencethrough the opening in the iirst end of said coarse ltering element tothe interiorv of the same and through said perforate side wall to saidoutlet, a fine ltering element in said second compartment having aninternal passage, a second outlet in the lower end of said casing-andmeans including a tube extending axially through the second end ofy saidcoarse filtering element and partition and forming a passageway to saidsecond compartment and the exterior of said fine filtering element,

`the interior passage of said fine ltering element having meansproviding communication with said second outlet. Y

2. In a lter, a generally cylindrical casing having a central axis andclosed ends, a header closing the upper end of said casing, said headerhaving an internal walll means coaxial of' said axis and defining achamber, there being an inlet in said header in communication with saidchamber, there also being an outlet in said header from the exterior ofsaid chamber, a partition in said casing forming upper and lowercompartments spaced along said axis, a coarse filtering element in saidupper compartment, said element having spaced imperforate closed endsand filtering material extending between and peripherally of said endsto denne an internal space, one of said ends having an opening thereinin communication with said inlet, resilient means yieldingly urging saidcoarse filtering element so that its upper end is in huid-tightengagement y ment, a fine filtering element in said lower com-A partmenthaving an internal passage in `communication with said second outlet anda tube having one end in the lower compartment and extending centrallythrough the ends of saidA coarse filtering element and said partitioninto the header, means providing a passageway from the chambercommunicating with the other end of said tube, said coarse filteringelement movable axially on and along said tube in response to apredetermined pressure in said chamber, to place said inlet and firstoutlet in direct communication about the end of said wall means. Y

3. A filter comprising a generally cylindrical casing having a centralaxis, one end of said casing having an internal wall means extendingabout said axis to form a chamber, there being an inlet in said endleading to said chamber and an outlet from said end exteriorly of saidcham- I ber, a partition dividing said casing into first and secondcompartments, spaced along said axis, a

coarse filter in said first compartment,'said fil ter having spacedimperforate end walls and filtering material extending peripherallythereof` tween said inlet and outlet about the end of said internal wallmeans, a second outlet in the other end of said casing, a fine filteringelement in said second chamber having means internally thereof incommunication with said second outlet, and means forming a passagewayaxially of said casing through the lower Wall ofV said coarse filteringelement and said partition to said second compartment, said finefiltering element including a normally closed valve in said internalmeans adapted to open in response to a predetermined pressure in saidsecond compartment to by-pass fluid directly from said secondcompartment to said second outlet.

4. In a filter, a generally cylindrical casing having a central axis anda closed lower end, a header closing the upper end of said casing, saidheader having internal wall means defining a chamber, there being aninlet in said header in communication with said chamber, there alsobeing an outlet in said header exteriorly of said chamber, a partitionin said casing forming first 6 Y and second compartments spaced alongsaid axis, a coarse filtering element in said first compartment andhaving a first end having an opening axially thereof, a second andimperforate end remote from said wall, and perforate side Walls,resilient means between said second end and partition yieldingly urgingsaid first end of said coarse ltering element into fluid-tightengagement with the end of said chamber wall means, whereby fluid passesfrom vsaid inlet to said chamber, thence through the opening in thefirst end of said coarse filtering element tothe interior of the sameand through said perforate side walls to said outlet, a fine filteringelement in said second compartment, a second outlet in the lower end ofsaid casing, andmeans including an open-ended tube extending axiallythrough the second end of said coarse filtering element and partition tosaid second compartment, said fine filtering element having meansproviding communication with said second outlet.

5. In a filter, a generally cylindrical casing having a central axis anda closed lower end, a header closing the upper end of said casing, saidheader having internal wall means defining a chamber, there being aninlet in said header in communication With said chamber, there alsobeing an outlet in said header exteriorly of said chamber, a partitionin said 'casing forming first and seco-nd compartments spaced along saidaxis, a coarse filtering element in said rst compartment and having afirst closed end having an opening therein, a second and imperforate endremote from said wall arid perforate side walls, resilient means betweensaid second end and partition yieldingly urging said first end of saidcoarse filtering element into fluid-tight engagement with the end ofsaid chamber Wall means, Y

. whereby fluid passes from said inlet to said chamber, thence throughthe opening in the'first end-of-said coarse filtering element to theinterior of the same and thro-ugh said perforate side wall to saidoutlet, a ne filtering element in said second compartment having aninternal passage a second outlet in the lower end of said casing,

Y and means forming a passageway from the in- `terior o'f saidA coarsefiltering element to said lower compartment, whereby a portion of thefiuid entering said coarse filtering element passes to said lowercompartment, thence through said fine filtering element to said secondoutlet.

6. A filter as claimed in claim l, said fine filtering elementcomprising a cylindrical filtering body, means mounting said body withits axis coincident with said central axis, there beinga plurality ofcircumferential axially-spaced grooves in said body, a plurality ofscrapers each fitting a respective groove in said filtering body, andmeans including said tube operable from the eX- terior of said casing,for rotating said scrapers as a unit to cause them to traverse saidgrooves and clean the same.

7. A filter as claimed in claim 2, said fine filtering elementcomprising a generally cylindrical filter body, coaxial of said casingand having axially-spaced, circumferential grooves, a pluralityv CECILG'oRDoN1 voKEs. y EDWARD ARTHUR s'roxEs.v

